Many people who have come here, and some who are still here,
have used one or both of those medications for their PN.

High doses of nortriptyline (or amitriptyline) are not usually necessary. And there is some new evidence that the --triptylines enhance peripheral nerve growth factors.

I tried amitriptyline last year briefly, but it made my blood sugar go up some. It didn't do much to my nighttime pain, but I didn't stay on it because of the blood sugar changes. I don't think they have that effect on everyone though.

I never took gabapentin. If it had been available back when I was severe, I probably would have tried it at least. But my pain issues are not severe anymore, so I have no desire to do it now.
There are meta study evaluations for gabapentin now available on the PubMed that claim only about 30% of pain patients respond to gabapentin. So keep that in mind.

This post discusses gabapentin and Lyrica (which are related and very similar)
http://neurotalk.psychcentral.com/post829091-8.html